1. Field of the Invention
The invention relates to hydrocarbon separation, specifically the separation of butene-1 from a feed mixture containing other C4 mono-olefins using a potassium exchanged type X zeolite.
2. Description of the Prior Art
It is known from U.S. Pat. No. 3,723,561 (Class 260/677AD), the contents of which are incorporated by reference, to separate butene-1 from hydrocarbon mixtures using zeolites X and Y.
The present invention is an improvement on the process described in that patent. The improvement is the discovery of a better desorbent for the process.
The teachings of this patent as to the types of desorbents which can be used are very broad, and include many desorbents which although operable are not as good as the desorbent claimed herein.
The prior patent mentioned, as specific desorbent materials which could be used, higher molecular weight olefins such as octene-1 or lower molecular weight olefins. All of these were capable of separation from butene-1. The use of mixtures of normal olefins and iso-paraffins was also disclosed, with a mixture of 20 LV% octene-1 and 80 LV% iso-octane being disclosed at column 4, lines 50-53. This was the desorbent of choice for liquid phase operations.
Extensive studies of various adsorbents taught in that patent showed that a potassium exchanged X-zeolite gave excellent results. Further testing of different batches of experimental adsorbents was conducted to confirm that different manufacturing procedures could be used.
In the course of the testing of these adsorbents produced by conventional methods, there were some surprising discrepancies in results. Repeating the tests, we noted that not all the test conditions were the same, specifically that the feed composition varied somewhat test to test, and also that the desorbent composition varied as well.
Further testing showed that the desorbent composition had a significant effect on the process. It was discovered that use of a cyclo-paraffin or cyclo-olefin diluent with the preferred hexene-1 desorbent gave a desorbent with ideal properties for commercial use.